Check docker daemon is alive in ping endpoint

handlers/ping.go

@@ -1,9 +1,12 @@
 package handlers
 
 import (
+	"context"
 	"log"
 	"net/http"
+	"time"
 
+	"github.com/docker/docker/client"
 	"github.com/play-with-docker/play-with-docker/config"
 	"github.com/shirou/gopsutil/load"
 )
@@ -11,6 +14,21 @@ import (
 func Ping(rw http.ResponseWriter, req *http.Request) {
 	// Get system load average of the last 5 minutes and compare it against a threashold.
 
+	c, err := client.NewEnvClient()
+
+	if err != nil {
+		rw.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Microsecond)
+	defer cancel()
+
+	if _, err := c.Info(ctx); err != nil && err == context.DeadlineExceeded {
+		log.Printf("Docker info took to long to respond\n")
+		rw.WriteHeader(http.StatusGatewayTimeout)
+	}
+
 	a, err := load.Avg()
 	if err != nil {
 		log.Println("Cannot get system load average!", err)